There are ports of "rar" and "unrar", the former is i386 binary-only.. the latter has source code available, but has a proprietary licence.
If you're in a situation where you need to extract an archive..
archivers/unrar does work.
You should never help proliferate the use of RAR/ZIP, the Windows programs "WinRAR" and "WinZIP" can read gzip/bzip2 compressed tar archives according to their websites, so I can't see any situation where you'll need to be able to create RAR/ZIP archives.
References:
http://www.winzip.com/wzdifs.htm
http://www.rarlab.com/otherfmt.htm